GCS Plugins: standardize on qint over int_t

We had a mixture of integer type definitions with a predominance
of Qt types.  This removes the mixture.
GCS Experimental: use Qt int type instead of stdint consistently

We had a mixture but a predominance of Qt types.  This makes it
consistent.
GCS: use Qt int type instead of stdint consistently

We had a mixture but a predominance of Qt types.  This makes it
consistent.
Qt: include qglobal.h instead of stdint.h

Since we are using Qt int types instead of stdint it is
no longer required.